#include<iostream>
#include<mutex>
using namespace std;
class Singleton
{
public:
	static Singleton* getInstance()
	{
		if (instance == nullptr) {
			instance = new Singleton();
		}
		return instance;
	}
private:
	static Singleton* instance;
	Singleton() {};
};
Singleton* Singleton::instance = nullptr;


int main()
{
	Singleton* s1 = Singleton::getInstance();
	Singleton* s2 = Singleton::getInstance();
	return 0;
}